1. Field of the Invention
The present invention relates to an engine vibration isolation system and an engine vibration isolation method for suppressing transmission of vibration to a vehicle body from an engine that can switch between a first running and a second running which differ in the number of cylinders that are cut off, by supporting the engine on the vehicle body via an active vibration isolation support system and controlling via a control portion an actuator of the active vibration isolation support system according to a vibrational state of the engine.
The present invention also relates to a control system and a control method for an active vibration isolation support system for suppressing transmission of vibration to a vehicle body from an engine that carries out cylinder cut-off running which combines one cylinder cut-off period and two combustion periods in one cycle, by supporting the engine on the vehicle body via the active vibration isolation support system, and controlling via a control portion an actuator of the active vibration isolation support system according to a vibrational state of the engine.
2. Description of Related Art
Japanese Patent Application Laid-open No. 2005-3051 discloses a device which suppresses vibration during a transitional period between all-cylinder running and cylinder cut-off running by appropriately setting a timing to switch control of an active vibration isolation support system during the transitional period, in a V6 engine in which a bank on one side can be cut off and which can switch between all-cylinder running where all six cylinders are in operation, and cylinder cut-off running where only three cylinders are in operation.
In some V6 engines, in addition to the normal all-cylinder running (V6 all-cylinder running), the operation can be switched between a cylinder cut-off running (L3 cylinder cut-off running) in which the engine runs as an in-line three cylinder engine with a bank on one side cut off, and a cylinder cut-off running (V4 cylinder cut-off running) in which the engine runs as a V4 engine with one cylinder in each of the two banks cut off.
During the transitional period for switching between V6 all-cylinder running and L3 cylinder cut-off running, since the ratio of the frequency of 3rd order vibration in V6 all-cylinder running and the frequency of 1.5th order vibration in L3 cylinder cut-off running is the integer 2, the vibration waveform of the transitional period is relatively simple, and control of the active vibration isolation support system does not become complicated. However, during the transitional period for switching between V4 cylinder cut-off running and L3 cylinder cut-off running, since the waveform of vibration of the engine becomes complicated as described later, there is a problem that it becomes difficult for the active vibration isolation support system to efficiently exhibit a vibration isolation effect.
Furthermore, Japanese Patent Application Laid-open No. 2003-113892 discloses a device in which, when a vibrational state of an engine is estimated from an angular acceleration of a crankshaft of the engine and operation of an actuator of an active vibration isolation support system is controlled based on the vibrational state, if the engine vibration is large and it is easy to estimate the phase (during cylinder cut-off running), then the operation of the actuator is controlled based on the estimated phase for the engine vibration, whereas if the engine vibration is small and it is difficult to estimate the phase (during all-cylinder running), then the operation of the actuator is controlled based on a preset phase for the engine vibration.
In some V6 engines, the operation can be switched between cylinder cut-off running in which the engine runs as an in-line three cylinder engine with a bank on one side cut off, and cylinder cut-off running in which the engine runs as a V4 engine with one cylinder in each of the two banks cut off.
However, when the V6 engine runs as a V4 engine with one cylinder in each of the two banks cut-off, the cylinder combustion interval is different from that of a proper V4 engine, and thus the vibrational state is also different. That is, in a proper V4 engine, the four cylinders are combusted at equal intervals; whereas in the virtual V4 engine in which cylinders of the V6 engine are cut off, the combustion intervals of the four cylinders that are not cut off are not equal to each other, and the estimated vibrational state for the engine may vary according to the way in which one cycle of vibration is determined, as described later in embodiments.